The present invention relates to the art of cleansing or laundering articles of apparel in a receptacle with fluid and agitation. The invention relates particularly to control systems for washing machines of the type in which the articles to be laundered are placed in a receptacle or tub which is then partially filled with water and the articles agitated in the water during a program which includes the addition of suitable washing aids, such as detergent, and rinsing with fresh water. A widely used version of such washing machine employs a tub open at the top with a central motor-driven agitator disposed to rotate or oscillate about a vertical axis for providing the desired agitation to effect washing of the clothes.
Typically, such washing machines employ separately connected water lines for hot and cold water, with individual valving mechanisms to control the flow of the water fill to have either hot, cold, or a mixture thereof for portions of the washing cycle or program. A common control system for such washing machines employs a programmer/timer which is set for a desired overall program interval and sequentially controls the activation and deactivation of the water fill valve and the agitator and centrifuging or spin operation of the receptacle for extracting the water from the clothes at the end of the washing program. Typically, the machine user sets the desired time for the washing program by rotating a knob or dial to set the position of a cam drum which is usually rotated through not more than one complete revolution for the program or cycle and sequentially activates a plurality of switches which control the various washing machine functions, such as the water fill valves and the agitate/spin motor during the program. This common type of washing machine control employs a timing motor which drives the cam drum for operating the machine function switches.
Where electronic control of a washing machine program is desired, a micro-computer receives inputs from user actuation of discrete function inputs, such as from a touch panel or a plurality of panel-mounted push buttons to select the desired program interval and selected combination of machine functions for the particular type of washing desired for the particular fabrics of the clothes to be laundered. Both of the aforesaid type washing machine control systems thus rely upon the users knowledge of the characteristics of the clothes to be laundered, such as degree of soil, amount of clothes, and type of fabric to select the appropriate program for effecting the washing.
It has been desired, however, to provide a washing machine which can automatically determine the appropriate length of washing cycle and the minimum amount of water required to effect complete laundering. This latter requirement is particularly important in locations where water is in short supply. In the typical household washing machine, the machine user rotates a knob or dial on the control panel to the desired position indicative of the machine program or cycle interval as a fraction of one full revolution of the dial or knob where an electromechanical program/timer is employed for selecting the machine program. Where electronic circuitry and particularly a micro-computer is employed for controlling the machine program, the user is typically required to provide numerous push button or touch-panel inputs to program the micro-computer for the desired time interval for the cycle in addition to discrete inputs for the selected types of machine functions, such as hot or cold wash, or shortened rinse or spin portions of the program. In the aforesaid typical electronically controlled washing machine, once the user has made the input selections to the electronic control circuitry, there is no visual indication during the progress of the program as to the time interval or remaining functions to be performed for the user to ascertain by a quick glance at the control panel. Thus, although it has been desired to provide electronic control of a washing machine, the rotating indication or "time-out" of the electromechanical timer control knob has provided a convenient and desirable ready indication of the state of the machine program which is readily visible to the user from the control panel.
It has thus been desired to provide for automatic control of a washing machine employing electronic control circuitry and particularly a micro-computer to eliminate an electromechanical machine function switch programmer and to provide for automatic determination of the machine program, including wash time and water fill. It has further been desired to provide for a readily visible indication of a control panel in such an electronically controlled machine such that the user can readily discern, from a glance at the panel, the state of the program. It has further been desirable to provide a washing machine which can automatically limit the amount of hot water introduced into the machine tub in order to limit the BTU content or energy consumed by the washing machine in order to conserve the energy required to heat the water to be used for washing. Such limiting of the thermal energy employed for the warm or hot wash water has become of recent concern in the face of increased cost of fuel or electric power for water heaters and the promulgation of regulations for residential energy consumption by various governmental agencies.
It is known to control the inlet water temperature of a washing machine by alternately cycling open and closed, i.e., by "bang-bang" control, the hot and cold fluid inlet valves. It has also been previously proposed to control the fluid inlet temperature by the use of a proportional mixing valve. Both of these techniques have been found unsatisfactory in terms of service life and manufacturing cost in mass production.